Low testosterone levels are associated with carotid atherosclerosis in men.

OBJECTIVE: To study the relationship between endogenous sex hormone levels and intima-media thickness (IMT) of the carotid artery measured by ultrasonography. DESIGN: Population-based cross-sectional study. METHODS: Sex hormone levels measured by immunoassay, anthropometric measurements and IMT was studied in 1482 men aged 25-84 years participating in the 1994-1995 Tromsø study. The data were analysed with partial correlation, multiple linear regression and logistic regression analysis. RESULTS: Linear regression models showed that total testosterone and sex hormone-binding globulin levels, but not calculated free testosterone, serum oestradiol or dehydroepiandrosterone sulphate levels were inversely associated with the age-adjusted IMT (P = 0.008 and P < 0.001 respectively). These associations were independent of smoking, physical activity, blood pressure and lipid levels, but were not independent of body mass index (BMI). Excluding men with cardiovascular disease (CVD) did not materially change these results. In a logistic regression model adjusted for the confounding effect of CVD risk factors, men with testosterone levels in the lowest quintile (<9.0 nmol L(-1)) had an independent OR = 1.51 (P = 0.015) of being in the highest IMT quintile. CONCLUSIONS: We found an inverse association between total testosterone levels and IMT of the carotid artery in men that was present also after excluding men with CVD, but was not independent of BMI. The clinical relevance of this, however, is uncertain and needs to be investigated in a clinical setting.

Age and sex differences in the relationship between inherited and lifestyle risk factors and subclinical carotid atherosclerosis: the Tromsø study.

BACKGROUND: Ultrasound measurement of carotid artery intima-media thickness (IMT) is regarded as a valid index of atherosclerosis. Age and sex differences in the distribution of, and risk factors for, IMT have not been investigated thoroughly. METHODS: In 1994-1995 a total of 6408 men and women aged 25-84 years living in the municipality of Tromsø, Norway, underwent ultrasound examination of carotid artery IMT and measurements of cardiovascular risk factors. RESULTS: Age, systolic blood pressure, total cholesterol, HDL cholesterol, body mass index, and smoking were independent predictors of IMT in both sexes. Fibrinogen levels and physical activity were associated with IMT in men only, whereas triglyceride levels were associated with IMT independently of HDL cholesterol in women only. A family history of cardiovascular disease (CVD) was an independent predictor of IMT in both sexes, also when controlling for traditional CVD risk factors. The magnitude of the association between most risk factors and IMT did not differ depending on age, but the effects of physical activity and triglycerides were more pronounced at higher age. CONCLUSION: These data suggest that there are significant age and sex differences in the distribution and the determinants of subclinical atherosclerosis.

Prediction of mortality by ultrasound screening of a general population for carotid stenosis: the Tromsø Study.

BACKGROUND AND PURPOSE: The extensive use of ultrasound examination of carotid arteries has revealed stenosis in many asymptomatic subjects, and clinical studies have shown that carotid stenosis is a risk factor for cardiovascular disease and death. However, information on stenosis as detected in a general population and its relation to mortality is scarce. The purpose of this population-based study was to assess whether carotid stenosis is a predictor of death. METHODS: In 1994 to 1995, 248 subjects with suspected carotid stenosis were identified among 6727 men and women 25 to 84 years of age who were examined with ultrasound. These subjects and 496 age- and sex-matched control subjects were followed up for 4.2 years, and the number and causes of deaths were registered. RESULTS: The unadjusted relative risk for death was 2.72 (95% CI, 1.57 to 4.75) for subjects with stenosis compared with control subjects. Adjusting for cardiovascular risk factors increased the relative risk to 3.47 (95% CI, 1.47 to 8.19). The adjusted relative risk in persons with stenosis and no cardiovascular disease or diabetes was 5.66 (95% CI, 1.53 to 20.90), which was higher than in subjects with stenosis and self-reported disease (1.79; 95% CI, 0.75 to 4.27). There was a dose-response relationship between degree of stenosis and risk of death (P=0.002 for linear trend). Carotid stenosis was a stronger predictor of death than self-reported cardiovascular disease or diabetes. CONCLUSIONS: Carotid stenosis is a strong and independent predictor of death.

5-HD abolishes ischemic preconditioning independently of monophasic action potential duration in the heart.

OBJECTIVE: Blocking of the KATP channel with either glibenclamide or 5-hydroxydecanoate (5-HD) has been shown to abolish the infarct reducing effect of ischemic preconditioning (IPC) in hearts from several species, but the results in rat and rabbit have been equivocal. In this study we investigated if 5-HD could abolish IPC in rat and rabbit and further if IPC or IPC + 5-HD were affecting action potential duration in the rabbit heart. METHODS: The rat hearts were isolated and retrogradely perfused on a Langendorff perfusion apparatus with Krebs-Henseleit buffer. The rabbit experiments were performed in an in situ model. Rat and rabbit hearts were subjected to 30 min regional ischemia by ligating a coronary artery followed by 120 min (rat) or 150 min (rabbit) of reperfusion. The preconditioning protocol was one or three cycles of 5 min ischemia plus 5 min reperfusion in the rat and one cycle of 5 min ischemia plus 10 min reperfusion in the rabbit. In the rat 5-HD was added to the reservoir before ischemic preconditioning in different concentrations, and in the rabbit 5-HD was given as a bolus 5 mg/kg intraventricularly 2 min before the preconditioning ischemia. In the rabbit epicardial monophasic action potential duration at 50 % repolarization (MAPD50) was measured at 1, 2 and 5 min in each of the ischemic periods using a contact pressure electrode. Infarcts were measured with tetrazolium staining and risk zone volumes with fluorescent microspheres. RESULTS: All data are presented as infarct size in % of risk zone volume (mean +/- SEM). In the rat 200 microM of 5-HD abolished the protective effect of one cycle of IPC (28.6 +/- 4.7 versus 8.4 +/- 0.8) and 500M of 5-HD abolished three cycles of IPC (50.7 +/- 7.8 versus 8.4 +/- 2.0). Control was 40.9 +/- 2.8. In the rabbit 5-HD abolished IPC (41.2 +/- 7.2 versus 8.1 +/- 3.2). Control was 53.5 +/- 12.4. MAPD50 were significantly more shortened compared to control at 1 and 2 min into the 30 min ischemia for the IPC and IPC+5-HD. CONCLUSIONS: We conclude that 5-HD abolishes ischemic preconditioning when given before the preconditioning ischemia in both rat and rabbit but does not abolish the ischemia induced shortening of the action potential duration in the rabbit; thus, a role for the mitochondrial KATP channel and not the sarcolemmal KATP channel in the protective mechanism behind IPC is probable.

Population-based study of age at menopause and ultrasound assessed carotid atherosclerosis: The Tromsø Study.

Early menopause has been associated with higher prevalence and incidence of cardiovascular disease and death than late menopause, indicating that early loss of ovarian function and subsequent deficiency of estrogen may promote such diseases. No population-based studies have, however, examined the relation between age at menopause and atherosclerosis. We assessed the prevalence and the extent of carotid atherosclerosis by high-resolution B-mode ultrasound in 2588 postmenopausal women who participated in a population health survey. Information about age at menopause and menarche, parity, use of hormone replacement therapy, and prevalent diseases was collected, and cardiovascular risk factor levels were measured. Women with late menopause and women who ever had used postmenopausal estrogens had significantly less atherosclerosis than women with early menopause and those with never use of estrogen. This study provides further support for the hypothesis that estrogen protects women against cardiovascular disease.

Sex differences in the relationship of risk factors to subclinical carotid atherosclerosis measured 15 years later : the Tromsø study.

BACKGROUND AND PURPOSE: Ultrasound measurement of carotid artery intima-media thickness (IMT) is regarded as a valid index of atherosclerosis. Determinants of IMT in cross-sectional studies have been established, but the long-term relationship between cardiovascular risk factors and subclinical atherosclerosis has not been investigated thoroughly. METHODS: We included in the study 3128 middle-aged men and women in Tromsø, Norway, who in 1980 attended the baseline examination with measurements of cardiovascular risk factors and who underwent carotid ultrasonography after 15 years of follow-up. RESULTS: Age, blood pressure, total cholesterol, HDL cholesterol, and body mass index were independent long-term predictors of IMT in both men and women. Triglyceride levels were associated with an increase in IMT in women only, while physical activity and smoking were predictors of IMT in men only. However, smoking was associated with increased risk of having atherosclerotic plaque in both men and women. There were no differences in the strength of risk factor effects on IMT in the common carotid artery and the carotid bifurcation. CONCLUSIONS: The present study indicates that established cardiovascular risk factors are independent predictors of subclinical atherosclerosis measured after 15 years of follow-up. However, there may be significant sex differences in the relationship between triglycerides, smoking, and physical activity and the risk of atherosclerosis.

Age and sex differences in the distribution and ultrasound morphology of carotid atherosclerosis: the Tromsø Study.

Atherosclerosis begins early in life and is the major underlying cause of cardiovascular morbidity and death. Yet, population-based information on age and sex differences in the extent and morphology of atherosclerosis throughout life is scarce. Carotid atherosclerosis can be visualized with B-mode ultrasound and is a marker of atherosclerosis elsewhere in the circulation. We assessed both the prevalence and the morphology of carotid atherosclerosis by B-mode ultrasound in 3016 men and 3404 women, 25 to 84 years old, who participated in a population health survey. The participation rate was 88%. Plaque morphology was graded according to whether a plaque was predominantly soft (echolucent) or hard (echogenic). Atherosclerotic plaques were found in 55.4% of the men and 45.8% of the women. In men, there was a linear increase with age in the prevalence of carotid atherosclerosis, whereas in women, there was a curvilinear age trend, with an inflection in the prevalence rate of women at approximately 50 years of age. The male predominance in atherosclerosis declined after the age of 50 years, the plaque prevalence being similar in elderly men and women. Men had softer plaques than women; this sex difference in plaque morphology increased significantly (P=0.005) with age. The sex difference in the prevalence of atherosclerosis and the female age trend in atherosclerosis show significant changes at the age of approximately 50 years, suggesting an adverse effect of menopause on atherosclerosis. The higher proportion of soft plaques in men compared with women increases with age and may partly account for the prevailing male excess risk of coronary heart disease in the elderly despite a similar prevalence of atherosclerosis in elderly men and women.

Equal reduction in infarct size by ethylisopropyl-amiloride pretreatment and ischemic preconditioning in the in situ rabbit heart.

UNLABELLED: Inhibition of Na+/H+ exchange with amiloride analogues has been shown to provide functional protection during ischemia and reperfusion and to reduce infarct size in isolated rat hearts. In rat hearts, treatment with ethylisopropyl-amiloride (EIPA, a selective Na+/H- exchange inhibitor) was additive to the protection afforded by ischemic preconditioning. In addition, such compounds have been demonstrated to reduce infarct size in in situ rabbit hearts. The aim of the present study was to determine to what extent preischemic treatment with EIPA could reduce infarct size in an in situ rabbit model of regional ischemia and reperfusion. We also wished to determine if this effect was additive to the infarct reducing effect of ischemic preconditioning. Anaesthetized, open chest rabbits, were subjected to 45 min of regional ischemia and 150 min of reperfusion. The risk zone was determined by fluorescent particles and infarct size was determined by TTC staining. Four groups were investigated: control, ischemic preconditioned (IP) (5 min of ischemia followed by 10 min reperfusion), EIPA (0.65 mg/kg iv given preischemically) and EIPA + IP. The main results expressed as percent infarction of the risk zone +/- S.E.M. for the different groups were: control 59.2+/-3.3% (n = 6), IP 16.3+/-2.1% (n = 6) (p < 0.001 vs. control), EIPA 16.9+/-4.1% (n = 5) (p < 0.001 vs. control), EIPA + IP 22.5 +/-9.5% (n = 6) (p < 0.001 vs. control). IN CONCLUSION: EIPA, when administered prior to ischemia, caused a reduction in infarct size in the in situ rabbit heart which was similar to that seen with ischemic preconditioning, however, the effect was not additive to ischemic preconditioning.

Lipid peroxidation, arachidonic acid and products of the lipoxygenase pathway in ischaemic preconditioning of rat heart.

OBJECTIVE: Preconditioning with brief intermittent periods of ischaemia is known to provide protection against ischaemic injury. It has been suggested that myocardial ischaemia also activates phospholipase A2, which releases arachidonic acid from phospholipids. In the present study the possible role of phospholipid peroxidation, arachidonic acid and products of the lipoxygenase pathway in cellular mechanisms of ischaemic preconditioning was examined. METHODS: Isolated, buffer-perfused rat hearts were freeze-clamped at the end of preconditioning (a cycle of 5 min global ischaemia +5 min reperfusion) and at the end of 30 min global ischaemia and analysed for non-esterified fatty acids and fatty acids in the 2-position of phospholipid. In a separate set of experiments, hearts pretreated with a lipoxygenase inhibitor, nordihydroguaiaretic acid (NDGA), were subjected to 30 min regional ischaemia and 120 min reperfusion. Infarct size was determined by tetrazolium staining and the ischaemic risk zone with fluorescent particles. RESULTS: Myocardial levels of arachidonic as well as of linoleic and docosahexaenoic acid were significantly elevated by preconditioning. Also, the level of peroxidized polyunsaturated fatty acids (measured as hydroxy conjugated dienes) in myocardial phospholipid was significantly increased: 101.4 +/- 16.8 nmol/g versus 51.2 +/- 7.3 nmol/g tissue dw in the control group, p < 0.05. Pre-treatment of hearts with 5 microM NDGA blocked the infarct limiting effects of preconditioning: infarct size was 37.4 +/- 6.4% of risk zone in control, 9.0 +/- 0.9% in the preconditioning group and 27.7 +/- 3.8% in the preconditioning + NDGA group (p < 0.05 vs. i.p., n.s. vs. control). CONCLUSION: Our findings provide evidence for the involvement of phospholipase A2 and lipoxygenase derived lipid second messengers in ischaemic preconditioning of the isolated rat heart.

Carotid intima-media thickness and plaque in patients with familial hypercholesterolaemia mutations and control subjects.

BACKGROUND: In individuals with familial hypercholesterolaemia (FH), ultrasonographic measurement of carotid intima-media thickness (IMT) and plaque may provide a non-invasive assessment of cardiovascular risk. METHODS: We examined carotid artery IMT and its determinants in 79 non-smoking, normotensive, treated men and women with FH aged 26-46 years, and in 79 non-smoking, normotensive sex-, age- and body mass index-matched control subjects. FH was verified by molecular genetic analyses. The underlying mutation in the low-destiny lipoprotein receptor gene included a splice-site mutation, mutations predicted or shown to lead to class 2B mutations or other mutations that probably represent class I mutations (null alleles). RESULTS: The carotid bifurcation and common carotid artery IMT was increased in men with FH compared with control subjects (0.81 +/- 0.15 mm vs. 0.74 +/- 0.19 mm and 0.61 +/- 0.13 mm vs. 0.55 +/- 0.14 mm respectively; P < 0.05). The carotid bifurcation IMT was increased in women with FH compared with control subjects (0.74 +/- 0.17 vs. 0. 66 +/- 0.15; P = 0.005). More subjects with FH had carotid plaque (54% vs. 14%; P = 0.0001). In multivariate analysis, male gender, level of low-density lipoprotein-cholesterol, cholesterol-years score and xanthoma were associated with IMT and plaque in subjects with FH. FH subjects with class 2B mutations had lower cholesterol levels than subjects with mutations belonging to the other classes. They also had a tendency towards a decreased common carotid artery IMT. CONCLUSION: These findings confirm the importance of gender, xanthoma and lifetime cholesterol levels in relation to carotid atherosclerosis in FH. Whether the type of mutation causing FH modulates carotid artery IMT and plaque requires further study.

Reproducibility of ultrasound assessment of carotid plaque occurrence, thickness, and morphology. The Tromsø Study.

BACKGROUND AND PURPOSE: Ultrasonography is increasingly used in vascular research, but there is limited information about the reproducibility of the ultrasound method for screening purposes. In this study the reproducibility of ultrasound assessment of carotid plaque occurrence, thickness, and morphology was examined within the setting of a population health survey. METHODS: In 1994/1995, 6720 participants in the Tromsø Study, Norway, underwent B-mode ultrasound scanning of the right carotid artery. The between- and within-sonographer reproducibility of ultrasound assessment of plaque occurrence and thickness was estimated by repeated scanning of a random sample of 107 participants. The between- and within-sonographer reproducibility of plaque morphology classification (echogenicity, four categories and heterogeneity, two categories) was determined by repeated reading of videotaped images of 119 randomly selected arteries with plaques. RESULTS: Between- and within-sonographer agreement on plaque occurrence was substantial with kappa values (95% CI) of 0.72 (0.60 to 0.84) and 0.76 (0.63 to 0.89), respectively. Reproducibility of plaque thickness measurements was moderate, with mean absolute differences ranging between 0.25 and 0.55 mm (coefficients of variation between 13.8% and 22.4%). Agreement on plaque morphology classification was high, with kappa values ranging between 0.54 and 0.73. CONCLUSIONS: Population screening using B-mode ultrasound provides a valuable means for the detection and morphological evaluation of carotid plaques, whereas measurements of plaque thickness are subject to considerable measurement error.

Reproducibility of ultrasonographically determined intima-media thickness is dependent on arterial wall thickness. The Tromsø Study.

BACKGROUND AND PURPOSE: We compared the reproducibility of B-mode ultrasonographic measurements of intima-media thickness (IMT) in various segments of the right carotid artery and examined whether measurement error was associated with IMT or cardiovascular risk factor levels. METHODS: In 1994/1995 a total of 6676 participants in the Tromsø Study underwent ultrasound examination of common carotid artery IMT. Reproducibility of measurements was assessed by inviting 111 participants to a second ultrasound scan within 3 weeks of the first scan. On each occasion the subjects were examined by three sonographers. RESULTS: The mean between-observer absolute differences in IMT in the far wall of the bifurcation and the near and far walls of the common carotid-artery were 0.15, 0.10, and 0.08 mm, respectively. The corresponding within-observer differences were 0.15, 0.10, and 0.06 mm, respectively. Approximately 70% to 80% of total measurement variability was due to differences among sonographers; the rest was attributable to within-reader variability. Measurement error increased significantly with increasing IMT: the increase was more than twofold over the range of measurements. Cardiovascular risk factor levels were not associated with measurement variability when we controlled for IMT. CONCLUSIONS: We conclude that B-mode ultrasound provides reproducible estimates of the IMT in both the near and far walls of the carotid artery. Although measurement error is generally small, it increases proportionally with the level of IMT.

Potassium channel blocker dofetilide does not abolish ischaemic preconditioning.

Ischaemic preconditioning (IP) is a powerful mechanism for infarct reduction. Enhanced K+ conductance and shortening of action potential duration in the early phase of the sustained ischaemic episode have been proposed as important factors in the IP mechanism for infarct reduction. We have investigated whether the potassium channel-blocking class III anti-arrhythmic agent dofetilide could abolish IP in an in situ rabbit heart infarct model. Dofetilide is a specific blocker of the delayed rectifier potassium channel and thus lengthens the action potential duration by reducing potassium conductance during repolarization. Anaesthetized, open-chest rabbits were subjected to 30 min of regional ischaemia and 180 min of reperfusion. The ischaemic risk zone was determined by fluorescent particles, and infarct size was determined by TTC staining. Three groups were investigated: control, ischaemic preconditioned (IP) and IP plus dofetilide-treated (IPdof). The preconditioning protocol was 5 min regional ischaemia and 10 min reperfusion. The IPdof group underwent the same preconditioning protocol but additionally received dofetilide 20 micrograms kg-1 i.v. during the first 2 min of the first reperfusion period. Compared to pre-drug values dofetilide increased monophasic action potential duration from 149.2 +/- 11.5 ms (n = 4) to 215.8 +/- 12.4 ms, supporting blockade of the delayed rectifier potassium channel. At the same time heart rate was decreased from 255.5 +/- 12.5 to 230.3 +/- 8.2. The results expressed as percent infarction of the risk zone +/- SEM for the different groups were as follows: control (n = 11), 42.4 +/- 7.1; IP (n = 6), 7.6 +/- 4.3 [symbol: see text]; IPdof (n = 7), 12.3 +/- 4.1 [symbol: see text] (*p < or = 0.05 vs. control). These results show that the potassium channel-blocking agent dofetilide given after the preconditioning ischaemia but before the sustained ischaemia does not abolish ischaemic preconditioning.

Mepacrine protects the isolated rat heart during hypoxia and reoxygenation--but not by inhibition of phospholipase A2.

Mepacrine (quinacrine) has in a number of studies been shown to protect the heart from ischemic injury, a protection commonly claimed to be due to inhibition of phospholipase A2. The aim of the present study was to investigate the effect of mepacrine 1 microM on isolated, buffer perfused rat hearts subjected to 60 min hypoxia and 30 min reoxygenation. We also wanted to clarify whether any cardioprotective effect was due to inhibition of phospholipase A2 or to other effects of the drug. Mepacrine led to a substantial fall in left ventricular developed pressure (LVDP) and coronary flow (CF) during normoxic perfusion. Treated hearts showed less increase in LVEDP and less fall in LVDP during the hypoxic period, and significantly fewer hearts stopped beating compared to untreated controls. Release of CK during hypoxia and reoxygenation was reduced in treated hearts compared to controls (19.9 +/- 3.8 vs. 73.1 +/- 13.3 IU, p < 0.05). Lipid analyses of the myocardium showed a significant increase in the total amount of non esterified fatty acids (NEFA) in both untreated and mepacrine treated hypoxic hearts compared to normoxic controls, but to a significantly lower level in the mepacrine treated hearts. However, contribution of polyunsaturated NEFAs to total NEFAs did not differ between the groups. Also, neither total amount of fatty acids nor amount of polyunsaturated fatty acids obtained from the 2-position of the phospholipid fraction differed between the treated and untreated groups. In an enzyme assay, mepacrine 1 microM did not inhibit phospholipase A2 activity. We conclude that in our model mepacrine protects the heart from hypoxic injury, but probably by another mechanism than inhibition of phospholipase A2 induced membrane damage.

Preischemic bradykinin and ischaemic preconditioning in functional recovery of the globally ischaemic rat heart.

OBJECTIVES: Substantial release of bradykinin has been demonstrated to occur during short periods of myocardial ischaemia in various species. The aim of the present study was to investigate the protective effect of bradykinin in ischaemia and whether bradykinin could be involved in ischaemic preconditioning in the rat heart. METHODS: Isolated, buffer-perfused hearts were subjected to 30 min of global ischaemia, followed by 30 min of reperfusion. Postischaemic functional recovery was recorded in the following groups: (1) control; (2) treatment with 0.1 microM bradykinin for 10 min before ischaemia (BK); (3) bradykinin treatment combined with pretreatment with the specific bradykinin B2-receptor antagonist, HOE 140; (4) ischaemic preconditioning by 5 min ischaemia +5 min reperfusion prior to sustained ischaemia (i.p.); and (5) ischaemic preconditioning combined with HOE 140 administration. RESULTS: Postischaemic myocardial function was significantly improved in both BK and i.p. groups (developed pressure 66.9 +/- 6.8 and 67.6 +/- 7.1 mmHg, respectively, vs. 43.1 +/- 5.9 mmHg in controls, P < 0.05). Pretreatment with 1 microM HOE 140 completely abolished the effect of bradykinin, while protection achieved by i.p. was unaltered by this drug. None of the protective interventions was associated with any significant improvement in myocardial adenosine triphosphate, creatine phosphate, glycogen, lactate or glucose tissue levels, detected either at the end of ischaemia or after 30 min of reperfusion. CONCLUSIONS: Bradykinin, acting via B2-receptors, can protect against postischaemic contractile dysfunction to a similar extent as i.p.. An involvement of B2-receptors in the ischaemic preconditioning phenomenon could, however, not be demonstrated.

Bradykinin protects against infarction but does not mediate ischemic preconditioning in the isolated rat heart.

The aim of the study was to test if pre-ischemic treatment with bradykinin can protect against infarction in an isolated rat heart model of regional ischemia and reperfusion, and if any such protection is dependent upon activation of protein kinase C (PKC) or mediated through the nitric oxide (NO) pathway. We also investigated if bradykinin B2 receptor activation, alone or in combination with activation of adenosine receptors and alpha-adrenoceptors, are involved in the infarct size reducing effect of ischemic preconditioning. Buffer-perfused rat hearts were subjected to 30 min regional ischemia and 120 min reperfusion. Risk zone was determined by fluorescent particles and infarct size by tetrazolium staining. Treatment with bradykinin (0.5 mumol/l) prior to ischemia significantly reduced infarct size in percentage of risk zone compared to control experiments (infarct size: 9.6 +/- 1.3% v 41.8 +/- 3.6%, P < 0.001). An inhibitor of NO synthesis, NOARG (100 mumol/l), did not interfere with the bradykinin induced protection (infarct size: 13.3 +/- 2.0%), while chelerythrine (2 mumol/l), an inhibitor of protein kinase C, reversed the effect of bradykinin (infarct size: 30.0 +/- 2.8%). NOARG did not influence infarct size in the control group (infarct size: 40.1 +/- 3.2%). Ischemic preconditioning with three cycles of 5 min global ischemia + 5 min reperfusion offered protection similar to bradykinin (infarct size: 8.4 +/- 2.0%). The bradykinin antagonist HOE 140 (1 mumol/l) reversed the effect of bradykinin (infarct size: 42.5 +/- 3.1%), but did not interfere with ischemic preconditioning (infarct size: 7.7 +/- 1.6%). Similarily, combined blockade of alpha-adrenergic, adenosine and bradykinin B2 receptors with p-benzamine (10 mumol/l). SPT (100 mumol/l) and HOE 140 did not interfere with ischemic preconditioning (infarct size: 7.8 +/- 1.1%). Thus, bradykinin can protect against infarction via protein kinase C, but independently of NO. A role for bradykinin in mediating ischemic preconditioning against infarction could not be demonstrated.

Endothelin-1 can reduce infarct size through protein kinase C and KATP channels in the isolated rat heart.

OBJECTIVE: Protection from ischaemic preconditioning (IP) is dependent on activation of protein kinase C (PKC), and preconditionings protection can be mimicked by stimulation of various membrane receptors which are known to activate PKC. It is well known that KATP channel activation is cardioprotective. We tested the hypothesis that preischaemic treatment with endothelin-1 (ET-1) can protect against infarction by a PKC-dependent mechanism and by activating KATP channels. METHODS: Buffer-perfused isolated rat hearts were subjected to 30 min regional ischaemia and 120 min reperfusion. Risk zone was determined by fluorescent particles, and infarct size by TTC staining. RESULTS: Treatment with ET-1 in a dose of 1 nM prior to ischaemia significantly reduced infarct size in % of the risk zone compared to the control group (infarct size: 14.1 +/- 2.6 vs. 41.9 +/- 3.4%), while ET-1 0.1 nM did not protect (infarct size: 40.9 +/- 3%). AS the protective dose of ET-1 resulted in a significant reduction of coronary flow, a control group with a similar preischaemic flow-reduction was included (infarct size: 48.1 +/- 4.2%). Both the nonselective ETA/ETB receptor antagonist bosentan (1 microM) and the ET(A)-receptor-selective antagonist BQ 123 (2 microM) abolished protection from ET-1 (infarct size: 43.3 +/- 3.5 and 41.3 +/- 3.3%, respectively), as did the PKC inhibitor chelerythrine (2 microM) (infarct size: 41.1 +/- 5.2%) and the KATP blocker 5-hydroxydecanoate (infarct size: 41.7 +/- 2.9%). None of the ET receptor antagonists bosentan and BQ-123 influenced infarct size alone (infarct size: 42.7 +/- 2.5 and 41.3 +/- 3.3%, respectively). IP, similarly to ET-1, reduced infarct size (infarct size: 6.1 +/- 1.4%), but the nonselective ET receptor antagonist bosentan did not interfere with preconditioning's protection (infarct size: 13.2 +/- 4.3%). CONCLUSIONS: ET-1 treatment prior to ischaemia can protect against infarction via ETA receptors by a PKC-dependent mechanism and by activating KATP channels, but ET does not mediate IP in the isolated rat heart.

Blockade of the KATP-channel by glibenclamide aggravates ischemic injury, and counteracts ischemic preconditioning.

Blocking of the KATP-channel with glibenclamide has been shown to abolish the infarct-reducing effect of ischemic preconditioning in dog and swine. In the rabbit the results have been divergent purportedly related to anaesthesia. The aim of this study was to investigate the importance of the KATP-channel in a rabbit model where anaesthesia was not a confounding factor. Isolated rabbit hearts perfused with a Krebs-Henseleit bicarbonate buffer were subjected to 30 min regional ischemia by ligating a coronary artery, followed by 120 min reperfusion. The preconditioning protocol was 5 min global ischemia and 10 min reperfusion. Glibenclamide (100 microM) was added to the perfusion solution before the preconditioning ischemia and stopped after 5 min regional ischemia. Infarcts were measured with tetrazolium staining and risk zones with fluorescent microspheres. The main results expressed as percent infarction of the risk zone +/- SEM for the different groups are as follows: control (n = 12) 26.8 +/- 3.2, ischemic preconditioning (IP) (n = 9) 7.3 +/- 1.5, (p < 0.05 vs. control), control + glibenclamide (n = 9) 46.9 +/- 7.3 (p < 0.05 vs. control), IP + glibenclamide (n = 10) 38.3 +/- 6.9 (p < 0.05 vs. IP). These results show that glibenclamide treatment aggravates ischemia. Also, under the influence of glibenclamide ischemic preconditioning was no longer effective in reducing infarct size in the isolated perfused rabbit heart.

Risk factors related to carotid intima-media thickness and plaque in children with familial hypercholesterolemia and control subjects.

To assess the relationship between risk factors for cardiovascular disease and early atherosclerotic changes in the carotid artery, we measured carotid intima-media thickness by B-mode ultrasonography in 61 boys and 29 girls 10 to 19 years old with familial hypercholesterolemia (FH) and 30 control subjects matched for age and sex. All were nonsmokers, and all the FH adolescents had a known mutation in the LDL receptor gene. Mean intima-media thickness in the far wall of the carotid bulb was greater (P = .03) in the FH group than in the control subjects: 0.54 mm (95% confidence interval [CI], 0.52 to 0.56) versus 0.50 mm (95% CI, 0.47 to 0.52). In the entire group, mean and maximum intima-media thicknesses in the carotid bulb were positively associated with levels of apolipoprotein B and fibrinogen after control for pubertal stage (r = .19 to .24; P < .05), as was male sex. Plasma total homocysteine was similar in the FH and control groups and was associated with mean and maximum intima-media thicknesses in the far wall of the common carotid artery and carotid bulb after control for pubertal stage (r = .22 to .28; P < .05). With the exception of the relation between plasma fibrinogen level and mean carotid bulb intima-media thickness, these associations were essentially unchanged in stepwise multiple linear regression analyses, allowing for the entry of BMI and level of HDL cholesterol into the analysis. Carotid artery plaque was present in 10% of the children with FH versus none of the control subjects. Children with plaque had a higher mean cholesterol-years score than children without plaque. These findings suggest that the classic lipid and hemostatic risk factors as well as plasma total homocysteine are associated with markers of early carotid atherosclerosis from the second decade of life. B-mode ultrasonography may prove to be a useful tool in risk stratification of children with FH.

Reduced infarct size in the rabbit heart in vivo by ethylisopropyl-amiloride. A role for Na+/H+ exchange.

Inhibition of Na+/H+ exchange with amiloride analogues has been shown to offer functional protection during ischemia and reperfusion and reduce infarct size in isolated rat hearts and intact pigs. The aim of the present study was to examine if pre- or postischemic treatment with ethylisopropylamiloride (EIPA), a selective Na+/H+ exchange inhibitor, could reduce infarct size in an in situ rabbit model of regional ischemia and reperfusion. Anesthetized, open-chest rabbits were subjected to 30 min of regional ischemia and 180 min of reperfusion. The risk zone was determined by fluorescent particles, and infarct size was determined by TTC staining. Preischemic treatment with EIPA (0.65 mg/kg) significantly reduced infarct size from 45.8 +/- 3.5% of the risk zone in the control group to 10.6 +/- 3.1% (p < 0.01). EIPA-treatment during the first part of the reperfusion period did not reduce infarct size compared to controls (41.9 +/- 3.5%). We conclude that EIPA, when administered prior to ischemia, reduces infarct size in the rabbit heart of in situ, a protection most likely due to inhibition of Na+/H+ exchange.